Vertical spiral elevators have been known and used for some time. The spiral elevators are driven by vibratory apparatus connected at the top, at the bottom and/or in between. Most such systems utilize brute force connections directly from the vibratory apparatus to the vertical spiral. A typical system is shown in the Carrier U.S. Pat. No. 2,927,683 wherein two parallel shafts are mounted directly on the base of a spiral elevator with differently phased eccentric weights on the shafts. The shafts are simultaneously driven in opposite directions of rotation by a common motor. Other systems are shown in the Roder et al U.S. Pat. No. 2,934,202, the Schrader U.S. Pat. No. 4,267,919 and the Spurlin U.S. Pat. No. 3,053,380. All of these systems require large motors to handle start-up and shutdown of the elevator and, due to the loads on the system, often experience broken drive shafts, worn bearings and the like.
In addition, the current and prior systems generally use constant speed motors and have the eccentric weights in a fixed position on the shafts so that the transient response at start-up and shutdown is very high resulting in frequent burnout of the motors.
Current units are mostly of the brute force type and employ couplings and/or gear boxes to positively drive the two shafts, upon which the eccentrics are mounted, in opposite directions and in a synchronized relationship. These systems require that each unit be preset relative to the other unit so as to get the synchronization desired.